We propose to develop a program based on our prior research that uses innovative Internet technology to provide a low cost, easily disseminated program that captures two critical elements of effective behavioral weight loss programs—namely, training in key behavioral weight control strategies and increased participant accountability. Patients, referred by their physician for weight loss, will be offered a 12 week program that they can view at their convenience on their computer. The program will use Web-based interactive multi-media approaches for presentation of the behavioral skills and provide a Web-based form for submission of self-monitoring and weight data; to maximize patient accountability, the program will include a system of automated feedback for participants, which comments on their weight loss to date and their performance within several behavioral weight-loss domains, with suggestions tailored to the characteristics and performance of the individual. Periodic reports on the patients' progress will also be sent to the referring physician. We will test this program in a randomized trial with 250 patients referred by their physicians who will be randomly assigned to either Internet Education (Control) (N=125) or to the Innovative Technology program (N=125). Participants in both groups will receive a 12 week Internet program of either basic weight loss education or the Innovative Technology program and will be weighed at the start and end of the 3 month program and at 3 month follow-up. The primary hypothesis is that patients who are assigned to the Innovative Technology program will achieve larger average weight losses than those in the control group over the 12-week program. Secondary hypotheses are that the Innovative technology group will adhere better over the 12-weeks (assessed by log-ins to the web site and self-reported changes in diet and activity) and achieve better weight losses at 6 months than the control group.